1. Field of the Invention
The present invention relates to a respiration diagnosis apparatus which can either extract information to distinguish between obstructive apnea and central apnea or automatically perform such differentiation.
2. Description of the Prior Art
Conventionally, among respiration monitors, a monitor which detects the existence of respiration by detecting temperature differences between inspired air and expired air via a thermistor heat sensor inserted in the nasal cavity, a monitor which uses a microphone to detect the sound of breathing at the throat, a monitor which detects changes in the volume of the chest and/or abdomen during respiration via changes in electrical impedance, a monitor which detects changes in chest and/or abdominal measurements via a pressure sensor, distortion sensor, etc., and a monitor which detects via a pulse oximeter reduction in oxygen saturation in arterial blood accompanying apnea, as well as combinations of these monitors, have been proposed. In addition, it has already been announced that it is possible to estimate pleural pressure from respiratory changes in pulse waves.
There are two types of sleep apnea: sleep obstructive apnea, in which the thorax (abdomen) moves, but respiration does not occur due to an obstruction in the airway; and sleep central apnea, in which the thorax (abdomen) does not move. The basic maladies of these respiratory maladies differ, and the methods of their treatment differ as well. In conventional devices containing a heat sensor in the nasal cavity or a pulse oximeter, it was impossible to differentiate between these types of apnea. In addition, monitors which detected changes in chest (abdominal) volume, or in chest or abdominal measurements, could not detect sleep obstructive apnea. Therefore, a combination of several types of sensors was necessary to distinguish between central apnea and obstructive apnea. Moreover, attachment of pulse oximeters and respiratory sensors on patients was often required, which both patients and physicians found uncomfortable and inconvenient.